This invention relates to a structure for fitting a cap made of synthetic resin onto the leading end of a shaft member made of metal such as a lock shaft inserted into a brake shaft in a side braking system of an automobile, for example.
Where the leading end of the shaft member made of metal such as the lock shaft is to be ornamented or covered by fitting the cap made of synthetic resin onto the leading end of the shaft member, as illustrated in FIG. 1, it has been customary to have a male screw thread 2 formed on the leading end part 1a of a metallic shaft member 1, separately have a female screw thread 4 for helical insertion therein of the male screw threaded leading end part 1a formed inside a synthetic resin cap 3, and to fit the cap 3 to the leading part 1a of the shaft member 1 by helical engagement of the female screw thread 4 and the male screw thread 2 on the leading end part 1a.
The conventional threaded fitting structure described above, therefore, ensures strong fitting of the cap 3 to the leading end part 1a of the shaft member 1.
Since the conventional threaded fitting structure requires the male screw thread 2 to be formed on the leading end part 1a of the metallic shaft member 1, however, the fabrication of the shaft member 1 of course is a highly troublesome work. Moreover, the cap 3 made of resin requires the female screw thread 4 to be integrally formed therein at the same time that the cap 3 itself is formed in a stated shape. Thus, the mold to be used therefor is unduly complicated and is very expensive. As a result, the cap 3 itself is very expensive.
Moreover, the conventional threaded fitting structure entails highly complicated fittting work because the cap 3, during the course of fitting to the leading end part of the shaft member 1, must be held fast and rotated about its axis.